A gas turbine engine, such as a turbofan engine, includes a fan section, a gas generator and a low pressure turbine for powering the fan section using a gas stream generated by the gas generator. For an axial flow machine, the gas generator typically includes a plurality of compressor stages, a combustor and a plurality of high pressure turbine stages downstream of the combustor. Typically, the gas generator receives some of the air that is pressurized by the fan section, compresses it, and passes it to the combustor, where heat is added by combustion. The resulting heated gases are passed to the gas generator turbine, which extracts power to drive the gas generator compressor. The output of the gas generator turbine is then supplied to the low pressure turbine, which extracts mechanical power for driving the fan section.
In order to increase the power output and efficiency of the gas turbine engine, it is desirable to supply the gases from the combustor at or near stoichiometric temperature for the fuel mixture. This typically requires the use of both sophisticated materials and cooling schemes, such as where cooling air is bled from the compressor and supplied to selected turbine airfoils and gas path components downstream of the combustor for cooling. The cooling of the turbine components, such as convection, impingement and film cooling, reduces the metal temperature of those turbine components, thereby reducing the degradation of material properties due to, for example, temperature and oxidative damage. Although the cooling air may thereby allow higher operating temperatures of the engine, the cooling air is also parasitic to the engine, since it is not directly used to produce power, e.g., thrust, and hence, it is desirable to reduce the amount of cooling air that is used.
The present application provides a novel and non-obvious turbine airfoil arrangement for a gas turbine engine and an improved method for cooling the turbine airfoil arrangement.